The present invention relates to the field of mass storage devices. More particularly, this invention relates to a disc drive which includes a slider having a roughened air-bearing surface.
One of the key components of any computer system is a place to store data. One common place for storing data in a computer system is on a disc drive. The most basic parts of a disc drive are a disc that is rotated, an actuator that moves a transducer to various locations over the disk, and electrical circuitry that is used to write and read data to and from the disk. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disk. The magnetic transducer translates electrical signals into magnetic field signals that actually record the data xe2x80x9cbits.xe2x80x9d
The transducer is typically housed within a small ceramic block called a slider. The slider is passed over the rotating disc in close proximity to the disk. The transducer can be used to read information representing data from the disc or write information representing data to the disk. When the disc is operating, the disc is usually spinning at relatively high revolutions per minute (xe2x80x9cRPMxe2x80x9d). A current common rotational speed is 7200 RPM. Rotational speeds in high-performance disc drives are as high as 10,000 RPM. Higher rotational speeds are contemplated for the future.
The slider is usually aerodynamically designed so that it flies on the cushion of air that is dragged by the disk. The slider has an air-bearing surface (xe2x80x9cABSxe2x80x9d) which includes rails and a cavity between the rails. The air-bearing surface is that surface of the slider nearest the disc as the disc drive is operating. Air is dragged between the rails and the disc surface causing an increase in pressure which tends to force the head away from the disk. Simultaneously, air rushing past the depression in the air-bearing surface produces a lower than ambient pressure area at the depression. This vacuum effect counteracts the pressure produced at the rails. The opposing forces equilibrate so the slider flies over the surface of the disc at a particular fly height. The fly height is the thickness of the air lubrication film or the distance between the disc surface and the transducing head. This film minimizes the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation.
The best performance of the disc drive results when the slider is flown as closely to the surface of the disc as possible. In operation, the distance between the slider and the disc is very small; currently xe2x80x9cflyxe2x80x9d heights are about 1-2 micro inches.
Information representative of data is stored on the surface of the memory disk. Disc drive systems read and write information stored on tracks on memory disks. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the memory disk, read and write information on the memory disks when the transducers are accurately positioned over one of the designated tracks on the surface of the memory disk. The transducer is also said to be moved to a target track. As the memory disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the memory disk. Similarly, reading data on a memory disc is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disk. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disc drives, the tracks are a multiplicity of concentric circular tracks. In other disc drives, a continuous spiral is one track on one side of a disc drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held accurately during a read or write operation using the servo information.
One of the most critical times during the operation of a disc drive occurs just before the disc drive shuts down or during the initial moment when the disc drive starts. When shutdown occurs, the slider is typically flying over the disc at a very low height. Just before shutdown, the slider is moved to a non-data containing area of the disc where it is landed. During landing, the slider skids to a stop. When the disc drive starts, the slider skids across the non-data containing portion of the disc until the velocity of the slider is sufficient to produce lift between the slider and the disk.
In the past, the surface of the disc was textured to keep contact points between the disc and the slider to a minimum. Currently, it has been found that disks with smooth surfaces have better magnetic characteristics. The recording density of the disc is highest when the spacing between the transducing head and the magnetic layer is minimized. By reducing the roughness or texturing on the disk, the spacing between the transducing head and the magnetic layer on the disc can also be reduced. When smooth sliders are landed on disks formed with a smooth surface, problems occur. One of the larger problems is that a stiction force occurs between the slider and the disc surface. Stiction is static friction and is proportional to the size of a meniscus formed by the lubricant on the disk. When a smooth slider lands on a smooth disk, the stiction forces are high. In some instances, the stiction forces may cause the slider to separate from the suspension. In other words, the stiction forces may be so high that the slider rips from the suspension to which it is mounted.
One solution includes reducing the contact area of the air-bearing surface. However, even when this is done, frictional forces due to stiction remain and affect the performance of the air-bearing surface and slider. Evidence of air-bearing instability has been observed.
The slider includes an air-bearing surface which has a contact area. The slider also includes a transducer. The transducer is typically located near said contact area. Another solution is to texture or roughen the contact surface of the air bearing surface to reduce stiction between the slider and the disc surface. Some in the industry refer to texturing the contact areas as slider integrated pads (SLIP). The roughened surface portion of the contact area is formed in one of several ways. The slider integrated pad solution has been very successful in reducing the formation of stiction between the slider and represents a technology path towards future higher density recording. Even so, stiction problems may still be encountered using the slider integrated pads (SLIP).
Typically, the slider in a disc drive flies at a slight angle or pitch. Current designs of the air bearing surface recess the rails or rear pads from the trailing edge in order to get the transducer in closer proximity to the trailing edge. A center pad may also be recessed from the trailing edge of the slider.
Due to the considerable amount of recess of the rear pads from the trailing edge, however, the slider may rest on the disc in a backward tipped state. A tipped head permits the formation of a large, high pressure meniscus (or menisci) under the center rail, and in certain cases under the side rails as well. As a result of the large normal force arising from these menisci, the head disc interface experiences an excessively large stiction force, or stiction failure.
There are multitudes of mechanisms that may lead to slider tipping. Backward rotation of the disc prior to its coming to a full stop coupled with a sufficiently large frictional force can tip the slider backward and cause the head to remain in the tipped state if a sufficiently large meniscus is formed immediately. Alternatively, if the slider collects a sufficient amount of lube at the trailing edge during flying, then, the lube droplet(s) may bridge between the air-bearing surface near the trailing edge and the disc surface to form a meniscus (menisci) during rest dwell, and the resultant meniscus force may tip the slider. Also, spacing loss between the air-bearing surface and the disc surface at the tailing edge of the slider due to disc waviness or rear of the center pad wear may create a condition that facilitates slider tipping. Of course, if some or all of these mechanisms may be at work simultaneously, the probability of slider tipping will be increased.
For current SLIP designs with recessed rear rails, head tipping is unavoidable. In order to mitigate the high stiction problem when tipping does occur, a scheme solution is needed to reduce or eliminate the meniscus force. There is also a need for a solution to the tipping problem that would either reduce or, preferably, completely eliminate tipping.
There is also a need for a method and apparatus that allows for use of a smooth disc so that the spacing between the transducing head associated with the slider and the disc can be controlled and kept to a minimum to provide for an enhanced recording density of the information stored on the disk. There is also a need for an apparatus that provides for reduced stiction forces and yet still provides a stable air-bearing surface and slider. The apparatus and method must also provide an air-bearing that is rugged and durable enough to last for the life of the disc drive.
An information handling system, such as a disc drive, including a base, a disc stack rotatably attached to the base, and an actuator assembly movably attached to the base. The actuator assembly also includes a load spring and a slider attached to said load spring. The slider for a disc drive includes a block of material having a leading edge, a trailing edge and an air-bearing surface. The air-bearing surface has at least one contact surface. Attached to the slider is at least one post for controlling the pitch of the slider. The post is movable between a first position and a second position. The post is attached to a piezoelectric element for moving the post between a first position and a second position. The post is actuated between the first position and the second position. In one embodiment of the invention, one post is attached to the trailing edge of the slider. In another embodiment of the invention, one post is attached to the first side edge of the slider near the trailing edge and another post is attached to the second side edge of the slider near the trailing edge. In other embodiments, more active anti-tipping posts are attached to the slider to control the pitch of the slider and prevent stiction due to the formation of a meniscus at the trailing edge of a tipped slider.
A suspension assembly for use in a disc drive includes a load beam and a slider attached to the load beam such that the slider can pitch and roll. The slider includes a body of material having a leading edge, a trailing edge, a first side edge and a second side edge. A post movable between a first position and a second position attached to the slider. The post may be attached to the trailing edge of the slider or to one of the first side edge or second side edge of the slider. Moving the post between the first position and the second position controls the pitch of the slider. The post includes a piezoelectric element having a portion of which is attached to the body of the slider and another portion of which is attached to the pad. The invention reduces stiction between the contact surface of the slider and the disc of the disc drive.
Advantageously, the active anti-tipping posts 600, 700, 710, 820, 830 located at the trailing edge of a slider 126 will completely eliminate slider tipping, thereby providing a solution to the tipping related high stiction problem seen with SLIP heads. At the same time, the slider""s flyability characteristics are preserved. Furthermore, the stiction forces produced between the surface of the disc and the slider are substantially reduced, thus allowing contact start stop of a slider onto a smooth disk. Furthermore, since a smooth disc can be used and stiction can be controlled enhanced recording densities may be achieved. The resulting air-bearing is rugged and durable.